This invention pertains to the art of continuous casting and more particularly to continuous casting die apparatus.
The invention is particularly applicable to a mandrel employed for continuous casting of generally tubular metallic members and will be described with particular reference thereto. However, it will be appreciated that the invention has broader applications and could be adapted for use in other environments by those skilled in the art. Typical of the metals continuously cast and to which the subject invention is particularly applicable are brass, aluminum, bronze and the like, although many other metals and alloys can also be advantageously continuous cast using the subject inventive concepts.
In continuous casting tubular members, two general types of casting systems are employed. The first requires the casting to move at a constant speed while the die reciprocates along the casting longitudinal axis. The die moves downward at the same or a greater speed than the casting and moves upwardly at approximately 3 times the descent velocity with the amplitude of reciprocation typically being 1/8" or less. The second method is one in which the die is stationary and the casting moves intermittently to effect the required casting conditions. During a withdrawal stroke, the casting moves fast enough so that only liquid metal enters the cooled length of the die, causing intimate die-metal contact. The stroke is followed by a dwell period during which the casting stops or slows down so that it will exit from the solidification zone at the proper temperature. The concepts of the subject invention are particularly directed and applicable to this latter system.
In such systems, it has been found particularly desirable to be able to provide a fairly compact die and mandrel arrangement which would also facilitate obtaining generally smooth inside and outside surface finishes on the continuous cast member and which would further facilitate the production of a member falling within acceptable tolerance ranges. To accomplish these ends, it has been found desirable to have the molten metal pass from a liquid to a solid state at a fairly precise area along the mandrel over a limited length thereof and to prevent the conduction of substantial heat flow from the uppermost area of the mandrel to the freeze or solidification area.
Prior attempts at obtaining such results have not proved entirely satisfactory. The subject invention, however, is deemed to fully meet these desires and provide a substantial improvement for mandrels employed in continuous casting of tubular metallic members.